Comparison of Sodium and Potassium Levels among COVID-19 Patients on Arterial Blood Gas Analysers and Clinical Chemistry Autoanalysers

Abstract

Introduction: The electrolytes and Arterial Blood Gas (ABG) analysis are the crucial part of the evaluation in Coronavirus Disease 2019 (COVID-19) patients. Hyponatremia and hypokalemia are the electrolyte imbalance, commonly seen in COVID-19 and hence, patients require serial monitoring of electrolytes. Variations of sodium and potassium levels between arterial and venous blood are known, however as per existing literature, there are no previous studies on the comparison of electrolytes in COVID-19 patients, when analysed in arterial and venous blood, by different methods and its significance in clinical practice. Aim: To determine whether the sodium and potassium levels of COVID-19 patients are comparable when simultaneously analysed in arterial whole blood and venous serum sample, by ABG analyser and chemistry Autoanalyser (AA) respectively. Materials and Methods: This prospective observational study was conducted among COVID-19 positive patients admitted in Medical Intensive Care Unit at a Tertiary Care Super-Specialty Hospital, Pune, Maharashtra, India, from February 2021 to June 2021. A total of 100 arterial and 100 venous blood samples of COVID-19 patients were analysed for sodium and potassium levels on Gem Premier 3000 Blood Gas Analyser and AutoQuant 400i chemistry AA. The statistical analysis was done by the Bland Altman method to assess the agreement between the method of measurement for sodium and potassium levels in arterial and venous samples. Shapiro-Wilk’s test was applied to check normal distribution and statistical variables in sodium and potassium values measured by two methods. Results: The mean values for sodium in arterial blood were 135.91±8.36 mmol/L and in serum was 140.26±8.49 mmol/L. The mean value of potassium in arterial blood was 4.12±0.76 mmol/L and in serum 4.41±0.67 mmol/L. Coefficients of variation for arterial and venous sample sodium level was 4.21 mmol/L and for potassium was 0.28, with bias (95% limits of agreement) of (4.96 to 3.46 mmol/L) and (0.35 to 0.21 mmol ⁄L), respectively. Conclusion: The present study found a significant difference in electrolyte levels when compared between arterial whole blood in ABG analyser and venous serum sample in chemistry autoanalyser in COVID-19 patients. So, the clinicians must be aware of these variations and the same has to be kept in mind, while interpreting the results in COVID-19.